1. Field of the Invention
The present invention relates to a semiconductor light emitting device structure and a method of fabricating the same. More particularly, the present invention relates to a semiconductor light emitting device structure having a nanocrystal structure and a method of fabricating the same.
2. Description of Related Art
Distinct from the light emitting theory of regular fluorescent lamps or incandescent lamps generating heat to emit light, semiconductor light emitting devices such as light emitting diodes takes advantage of the specific property of semiconductor to emit light, and thus the light emitted by light emitting diodes is referred to as cold luminescence. The light emitting diodes have advantages of long service life, light weight, and low power consumption, and being free of harmful substance such as mercury, so the light emitting diodes used instead to illuminate can save a large amount of energy.
Currently, a nanocrystal light emitting diode is proposed to improve the light emitting diode. Researchers found that like the frequency band structure in the state of electromagnetic wave being transmitted in periodic dielectric, a photonic band substance can be achieved by the periodic changing of more than two kinds of materials with different refraction index (or dielectric constant), thereby paving a way for developing the above nanocrystal light emitting diode.
FIG. 1 is a schematic sectional view of the conventional nanocrystal light emitting diode, in which a periodically arranged nanocrystal structure is fabricated on the semiconductor layer on the light emitting layer.
Referring to FIG. 1, the conventional light emitting diode mainly includes a substrate 100, an N-type GaN layer 102, a P-type GaN layer 104, a light emitting layer 106, a transparent conductive layer 108, electrodes 110, 112, and an insulating layer 114, wherein the surface of the P-type GaN layer 104 has a pattern 104a. The N-type GaN layer 102 and the P-type GaN layer 104 are successively disposed on the substrate 100, and the light emitting layer 106 is disposed between the N-type GaN layer 102 and the P-type GaN layer 104. The transparent conductive layer 108 is disposed on the surface of the P-type GaN layer 104, and the electrodes 110 and 112 are respectively disposed on the N-type GaN layer 102 and the transparent conductive layer 108, wherein the insulating layer 114 is disposed beneath the transparent conductive layer 108 and separates the electrode 112 and the P-type GaN layer 104.
The nanocrystal mainly functions as changing the refraction of light, such that the light emitted from the active light emitting layer can be successfully sent out, and is not totally reflected inside the light emitting diode. Therefore, the nanocrystal light emitting diode has higher extraction efficiency than the conventional light emitting diode.
However, the pattern 104a (i.e., the nanocrystal structure) of the P-type GaN layer 104 is usually fabricated in manner of etching, such that the defect density at the etched portions increases, leading to the increase of resistance, thus influencing the electrical property of the light emitting diode.